Hermetic crystal holder



Dec- 4, 1951 M. N. GLICKMAN ETAL HERMETIC CRYSTAL HOLDER Filed Nov. 30,1950 Patented Dec. 4, 1951 2,577,576 HERMETIC CRYSTAL HOLDER Mannes N.Glickman and Michael Klebanoii,l

N Utley, N. J

Application November 30, 1950, Serial No. 198,312

This invention relates to piezoelectric crystal units, and moreparticularly to holders for such crystals.

The present invention is concerned with crystal holders of the typecomp-rising a metal base and a hollow metal cover which is soldered tothe base. The base is formed with extrusions in which metal pins arelocated and maintained in insulated relation to the base by means ofglass seals. The crystal unit is mounted and electrically connected tothe inner ends of the metal pins. The mounted crystal is protectedagainst the deleterious effect of moisture, dirt, and the like, by themetal cover which is soldered to the base to provide a hermeticallysealed unit for the crystal. The externally projecting portions of themetal pins provide electrical connecting means which are insertable insocket type connectors which form part of the electronic circuit inwhich the crystal unit is to function.

Conventional crystal holders of the type described are utilized inspaces of restricted dimensions, are subjected to rough treatment whenbeing inserted into socket type connectors, and otherwise must becapable of precision performance under .varied conditions. Accordingly,it has been. necessary to set up standards relating to dimensions,tolerances, materials, minimum mechanical and electrical specifications,and the like, in order to assure the production of a high qualityproduct which insures optimum operational characteristics of theelectronic circuits with which such crystal units are associated. Suchstandards have been formulated by the Radio Manufacturers Associationand the Armed Services Procurement agencies and are recognized andobserved by suppliers of such electronic components.

One of the disadvantages of crystal holders known in the art, relates tothe low mechanical strength of the glass seal at the metal pins of theholder. In many instances, the receptacle portions of the socketconnector make an overtight lit with the pins on/ a holder, or there maybe a very slight misaligmnent between one or more pins and thecorresponding receptacle portions of the socket connector. ln eithercase, the glass seal at the pins is severely strained when the holder isplugged into the socket connector. The strain may be sufcient tofracture the seal, thereby leaving the crystal within the holder subjectto the adverse effects of moisture, dirt or the like.

In addition, it has been found that the glassmetal seals in conventionalcrystal holders, when 3 Claims. (Cl. 171-327 inserted into the socketconnector, fail to Withstand stresses due to vibration. Such stressesare diicult to avoid in cases of mobile electronic equipmentinstallations which must include crystal frequency stabilizing means.

It has been found that the relatively low resistance of glass-metalseals in conventional crystal holders, to mechanical strains isattributed to the form and distribution of the vitreous material inrelation to the metal base member and metal pins of the holder.

Accordingly, an object of this invention, is to provide in crystalholders of the type described, an improved form of base, wherein thevitreous material used to seal the metal pins to the base, isdistributed in a manner to 'render the glass'- metal seal at the pinshighly resistant to mechanical stresses or strains, however induced. Inparticular, the pins on the base' of the instant invention may beconsiderably 'bent without affecting the glass seal. In addition, suchseals are adapted to pass the rigorous vibration tests set out in thespecifications of the Armed Services Procurement agencies.

Since the dimensions of the crystal holders of the type described, mustbe held within standard dimensions and close tolerances,v any changes indesign must come within such' dimensional tolerances. Accordingly,another object of this invention is to provide a crystal holder basewherein the location and spacing of the metal pins is unchanged; theoverall dimensions of the holder including the base, is unchanged; thebase may have its peripheral portions selectively modified to engagealternative forms of covers, keeping within standardized dimensions andallowing the use of alternative soldering procedures for securing thebase to the cover.

A further object of this invention is to provide an improved crystalholder base which includes an extended, flat body of vitreous materialof substantially uniform thickness, in combination with spaced metalmembers sealed within the body, and a metal rim portion sealed to theperiphery of the body, the metal members, vitreous body, and metal rimhaving substantially the same thermal coefficient of expansion, and thethickness and extent of .the vitreous body being such as to providesubstantial resistance to mechanical stresses and strains which may beapplied to the metal members.

vIn conventional crystaly holders, the base is made of a stamped metalalloy having substantially the same thermal expansion coe'icient as thevitreous material used to seal the metal pins on the base, as well asthe pins themselves. Such alloy bases cannot be readily soldered to themetal cover of the holder unlessthe bases are precoated or plated withmetals or alloys which allow the soldering operation to be performed.The base is soldered to the cover after the sensitive crystal blank hasbeen mounted on the base. At the soldering temperature there is arelease of gases occluded when the metal alloy base is precoated orplated, as described. Such gases, when released within the holder, loadthe crystal blank and since the crystal blank is exceedingly sensitiveand delicate, the gases contaminate the blank so as to adversely aiectthe .performance of the crystal unit.

Accordingly, still another object of this invention is to provide animproved base for a crystal holder which comprises primarily, anextended, ilat vitreous body having metal pins or terminals sealedtherein, for mounting a piezo crystal in opposed relation to a centralportion of the vitreous body, in combination with a limited amount ofmetal alloy having the same thermal expansion coefficient as thevitreous body and taking the form of a rim member confined to theperiphery of the body and sealed thereto, the rim providing means forsoldering the base to the cover and exposing a minor amount of precoatedmetal alloy on the interior of the holder around the exposed innersurface of the vitreous body, thereby substantially eliminating apossible source of crystal contamination during the soldering operation.

Still another object of this invention is to provide a piezoelectriccrystal holder having improved electrical characteristics, wherein theholder base includes a pair of spaced metal pins adapted to beelectrically connected to a piezo crystal and mount the same within theholder, the pins being maintained in spaced relation by an extended,integral vitreous body, the total amount of metal other than the pins,being kept at a minimum by limiting such metal to a rim member sealed tothe peripheral portions of the vitreous body, whereby to substantiallyreduce the electrical capacitance of the holder, thereby improving theoperational characteristics of the piezo crystal unit.

Still a further object of this invention is to provide an improved basefor crystal holders which comprises a metal wall having a peripheral rimfor engaging the holder cover, the wall being formed with spacedopenings for positioning metal pins therein, the pins being maintainedin such positions by an extended vitreous body of substantially uniformthickness which is sealed to the wall and rim, thereby providing maximumresistance to mechanical stresses which may be applied to the pins, theinner surface of the metal wall providing means for attaching a crystalmounting bracket or the like.

Yet another object of this invention is to provide in a crystal holder,an improved base comprising an extended vitreous body with at least onemetal member extending transversely of the body in sealed relationthereto and metallic means engaging at least the peripheral portions ofthe body to provide means for soldering the base to the holder cover, atleast one of the metal members being hollow to provide conduit means forthe passage of conductors into the interior of the holder and/or meansfor exhausting the interior of the assembled holder. v

A further object of this invention is to provide an improvedpiezoelectric crystal holder which comprises components which areeconomical to manufacture, such components being quickly andeconomically assembled which is adapted to pass the most rigorousmechanical and electrical test requirements standardized in the art;which is rugged and which result in improved operational characteristicsfor the crystal mounted therein.

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

The invention accordingly consists in the features of construction,combinations of elements and arrangement of parts, which will beexemplied in the constructions hereinafter described, and of which thescope of application will be indicated in the following claims.

In the accompanying drawings:

Fig. l is a side elevational view of a conventional crystal holder, thebase being separated from the cover, with parts in section;

Fig. 2 is a side elevational view of a crystal holder embodying theinvention, the base and cover being assembled with parts broken away andparts in section;

Fig. 3 is an end elevational view thereof;

Fig. 4 is a partial side elevational view thereof showing amodification;

Fig. 5 is a side elevational view similar to that of Fig. 2, showing thecrystal mounted within the holder;

Fig. 6 is a perspective view of the upper portion of the holder shown inFig. 2;

Fig. 7 is a side elevational view of a holder base embodying theinvention and showing a modii'lcation thereof;

Fig. 8 is a side elevational view of a further modincation of a holderbase embodying the invention.

Referring in detail to the drawing and particularly to Fig. 1, iBdesignates a conventional holder for a. piezo crystal. The samecomprises a stamped metal base member il and a hollow cover member i2.The member Il is made of metal alloys known in the art which may becomposed of nickel, iron and cobalt, or other suitable alloys known inthe glass-metal sealing art. The member i I includes a ilat wall portioni3 which is formed with spaced openings it. The openings It are dened bydrawn metal as at i5 and which is substantially cylindrical in form. Themember ii further includes an upstanding peripheral flange i6 which hasan inverted U- shaped cross section.

Metal pins or terminals I7 are located within the openings M and aremaintained in spaced relation to the metal i5 by means of glass sealsi8. It is understood that the metal member il. the pins H and the glassseals le have substantially the same thermal expansion coemcient.

The cover i2 may be drawn from a suitable metal such as brass, nickelsilver, or the like. After a piezo crystal, not shown, is suitablymounted on the inner portions ila of pins il and electrically connectedthereto, the mounted crystal is housed in cover i2. This is accomplishedby engaging the upper portions of the cover walls with the ange i6 onbase il with a sliding iit. The base and cover are then solderedtogether at contacting portions in order to hermetically seal theassembly. Since the metal alloys of which base il are formed, do notlend themselves to soldering. the base members are provided withselected metal coatings or platings which make soldering easier.

It has been found that in bases of standard dimensions, the limitedcross section of vitreous material I8 at pins |1 has very littleresistance to mechanical strains. This is particularly noted when theholder is inserted or withdrawn from a socket connector having tightfitting receptacles, or when the pins are slightly misaligned with theirrespective socket rreceptacles, in which case, a pin may be slightlybent, as indicated in dotted lines in Fig. 1, when the holder isinserted into the socket connector. Also, the glass seal |8 has noresistance to vibratory stresses when the holder is inserted into thesocket connector.

Accordingly, there is provided an improved crystal holder assembly Illa,as shown in Fig. 2, comprising a base Ila and a cover |2a. The coverI2a, which may be drawn from brass, nickel silver, or the like,comprises a peripheral wall I9 upstanding from a bottom wall 20. Thewall I9 is formed at its open end with an outwardly olfset peripheralportion 2| which provides a seat 22 for the purpose hereinafterappearing.

The base ||a comprises an extended, integral body 23 of vitreousmaterial such as borosilicate glass or other glass known in theglass-metal sealing art. The body 23 is of uniform thickness and has amarginal outline complementary to the opening in cover |2a. The body 23includes opposite surfaces 24, 25 and a peripheral edge 26. A pair ofspaced metal pins or terminals 21 are sealed transversely of the body23, inwardly of edge 26. It will be apparent from a consideration of theligure, that the body 23 at the portions thereof immediately adjacentpins 21 has a thickness substantially equal to the thickness of otherportions thereof.

The body 23 is provided with an endless metal rim member 30, which issealed to the periphery and marginal portions of one surface thereof.'I'he member 30 is formed of a glass-metal sealing alloy well known inthe art and has a thermal expansion coeilicient substantially equal tothat of the metal pins 21 and the glass of body 23. The member 30 has asection in the form of a right angle, providing a continuous horizontalportion 3| and a continuous vertical portion 32. As shown in Fig. 2, theportion 32 has a depth substantially equal to the thickness of body 23and is sealed to the edge 26 thereof. The rim portion 3| extends towardthe pins 21 but the inner edge thereof terminates in spaced relation tothe pins. The rim portion 3l is sealed to marginal portions of surface24 of body 23. The member 30 is provided with a coating of metal so asto allow the member to be soldered.

A piezoelectric crystal generally indicated at C, is mounted on theinner portions 21a of the pins 21, in a manner known in the art, thecrystal being electrically connected to the pins. The mounted crystal ispositioned within cover I2a, the rim 30 being received within offsetwall p0rtions 2| of the cover and seated on seat 22 thereof. With thebase and cover in assembled relation, the upper edge 33 of cover wallportion 2| projects slightly above rim portion 3 I. A continuous solderseal 34 applied between adjacent portions of the rim 3|] and cover wallportion 2| hermetically seals the crystal C within the holder Illa, asshown in Fig. 5.

In the eventthat it is desired to evacuate the holder assembly, the body23 has a short tubular metal member 35 sealed transversely thereof, asshown in Fig. 4. The metal of member 35 has the same thermal expansioncoeilicient as the glass of body 23. After withdrawing air from theinterior of the holder |0a, the open end of member 35 is sealed by meansof a spot of solder, a soldered rivet, or the like.

It has been found that the pins 21 of holder |0a which providefrictional circuit contact members for the mounted crystal C, may besubjected to severe treatment without affecting the glass seal. Thus,the pins 21 may be bent or otherwise strained without cracking orotherwise impairing the vitreous body 23. Such crystal holders may beused with socket connectors having tight tting receptacles orreceptacles slightly misaligned with the pins, so as to require greatforce for inserting the holder in, or withdrawing the same, from thesocket connector, without ad versely affecting the glass-metal seals.

It will be noted from a consideration of Figs. 2, 3 and 6, that the basemember Ila is predominantly of a vitreous material, the metal other thanpins 21, being coniined to the rim member 30. The member 30 has itsportion 32 only, disposed within the interior of the holder, the bodysurface 25 presenting a non-metallic surface. Accordingly, with theprecoated metal exposed within the holder, so limited, the chances ofcrystal blank contamination by gases released from precoated metalsurfaces, during the soldering operation which seals the cover to thebase, are materially reduced.

In addition, it has been found that the electrical capacitance of theholder 10a is substantially reduced inasmuch as the metal present in thebase member is at a minimum. The reduced capacitance of holder |6aconsiderably improves the operational characteristics of the crystal C.

In the event that it is desired to provide a holder assembly using astraight wall cover, such as shown in Fig. l, such cover has a base 36,shown in Fig. 8, associated therewith. Base 36 comprises a vitreous body23 having surfaces 24, 25 and a peripheral edge 26, as previouslydescribed. Spaced metal pins 21 are sealed within body 23, inwardly ofedge 26. A metal rim member 31 is sealed to the peripheral portions ofbody 23. Member 31 comprises an inverted U-shaped portion havingdownwardly extending arms 38, 38a and a short, horizontally disposedportion 39 extending inwardly from arm 38a. The inner surfaces of arm38a and portion 39 are sealed to edge 26 and marginal portions ofsurface 25, respectively. Portion 39 terminates short of pins 21.

Thus, the base 36, having a crystal blank mounted on the inner ends ofpins 21, may be assembled with a cover I2, the open end wall portionsbeing received in the U-shaped flange of the base and sealed bysoldering. The completed unit will show high resistance to mechanicalstrain and substantial freedom from crystal contamination.

The high strength glass-metal seal of an extended vitreous body, mayalso be used in combination with a walled metal base, as shown in Fig.7. The base 40 comprises a metal wall 4| formed with a peripheral,upstanding flange 42, of inverted U-shaped section. The wall-4| isformed with spaced openings 43 in which are located the metal pins 44.The pins 44 are maintained in insulated relation to wall 4| by means ofan extended, integral vitreous body 45 which is sealed to the surface 46of wall 4| and the inner portion of flange 42. The body 45 is ofsubstantially uniform thickness and permits the pins 44 to be severelystrained without affecting the glass seal, as previously described.

'I'he base 40 may be used with a cover as shown in Fig. 1, the flange 42receiving the upper edge of the cover I2 and being soldered thereto, aspreviously described. The wall 4| of base 40 ail'ords means for mountinga bracket 41 by securing the same to surface 48 of the wall. The bracket41 is secured to wall 4| in a manner to space the bracket from the pins44 and the periphery of the wall. It will be noted that the metal ofwall 4| does not have to be drawn at openings 43 to provide cylindricalportions for holding the glass seal, as indicated in Fig. 1.

It is understood that the solid metal pins 21, 44 may be replaced inwhole, or in part, by tubular metal members which provide conduit meansfor conductors or the like which are to be introduced within the cover.Such conduits may also be used for evacuating an assembly. The assemblyis completed by applying solder seals or the like, to the open ends ofthe tubular members.

It will be apparent that there has Abeen provided a device in which theseveral objects of this invention are achieved and which is adapted tomeet the conditions of use.

As various possible embodiments might be made in the above describedinvention, and as various changes might be made in the embodiments aboveset forth, it is understood that all matter herein set forth or shown inthe accompanying drawing, is to be interpreted as illustrative and notin a. limiting sense.

Having thus described our invention, we claim as new and desire toprotect by Letters Patent:

1. A piezoelectric crystal device comprising a hollow metal casing openat one end, a hermetic seal for the open end of said casing comprising athin flat vitreous body of substantially uniform thickness; a pair ofspaced terminal members extending through and sealed to said body, ametal rim member sealed to peripheral portions of said body, said rimmember including a portion sealed to the peripheral edge of said bodyand terminating at one face thereof so as to leave a maximal area of thevitreous body exposed to the interior of the casing, a crystal mountedon the ends of said terminal members extending from said last mentionedface of the body, the portions of said terminal members extending fromthe other face of the body being frictional contact means for connectingsaid mounted crystal in an external circuit and subject to mechanicalstrains arising from supporting said device, said rim member engagingthe open end of said casing and a solder seal uniting said rim member tosaid casing, said vitreous body, terminal members and rim member havingsubstantially the same coeflicient of expansion.

2. In a crystal holder as in claim 1, wherein i said metal rim membercomprises a portion of U-shaped cross section opening toward the crystalside of said body.

3. In a crystal holder as in claim 1, wherein the Wall portions of saidcasing at the open end thereof are oiset outwardly to provide aperipheral seat and said rim member is positioned in said seat.

MANNES N. GLICKMAN. MICHAEL KLEBANOFF.

REFERENCES CEIED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain Sept. 9, 1947

